books.google.com - This is a thoroughly updated and revised edition of our highly acclaimed university textbook on the science of parapsychology. The objective of this book is to provide an introductory survey of parapsychologists' efforts to explore the authenticity and bases of anomalous, apparently paranormal phenomena....http://books.google.com/books/about/An_Introduction_to_Parapsychology_5th_ed.html?id=E3EzxyOufbgC&q=factors&utm_source=gb-gplus-shareAn Introduction to Parapsychology, 5th ed.